The present invention relates to a data distribution system for distributing data to a radio terminal, and especially, to a data distribution system capable of suitably providing necessary information to a radio terminal.
A radio terminal such as a mobile type telephone set and so forth not only can utilize a function for making a call and transmitting an electronic mail, but also can store various kinds of information in an internal memory and utilize this stored information. For example, utilization is one example, in which map information is stored in a memory in advance, and this is used at arrival to a destination. Although such several kinds of information can be stored in a memory in a radio terminal, especially in case of a mobile type device, capacity of a memory is restricted and information which can be stored is not so much. Accordingly, a method is widely adopted, in which information is stored in a memory each time by utilizing a communication function of a radio terminal. Also, from a viewpoint where updated information is utilized, a method is effective, in which such necessary information is down-loaded at a necessary time point.
Also, push type distribution service is given attention. In such push type distribution service, a user does not obtain information by especially having access to a content server of internet, and registered information is automatically sent to a radio terminal of a user. On the other hand, in JP-A-136365/1999, a high capacity memory is built in a mobile terminal, and contents which a user desires are distributed by a communication provider system and are automatically stored in the memory. At this time, in case that there is enough time until time when distribution is desired, a time band where a load is less is selected by taking traffic of communication into account, and distribution is executed, and thereby, economical distribution can be realized. As a result, a user stores contents in a memory until desired time, and can reproduce them whenever he or she wants. Also, in case that information stored in a memory increases and a storage region for new information becomes less, it can be suitable deleted.
However, in a technology described in JP-A-136365/1 999, it is assumed that the high capacity memory is built in the mobile terminal. Accordingly, unless such a high capacity memory is provided, time margin for information storage becomes less, and cost-up of hardware is certainly introduced. Supposing that capacity of a memory to be built in is small, if contents are distributed in a duplicate form in time, a space in the memory is lost, and after that, a situation occurs that other information cannot be obtained. As a result, there is a possibility that a situation occurs where distribution is conducted after scheduled time.
In case that such a situation occurs, even though map information is required by a reason why a user wants to see a map of a station area when the user arrives at a Tokyo station for example, inconvenience that this information cannot be received at arrival time to the Tokyo station occurs. Accordingly, a case in which information obtained with much trouble is not at all useful appears. Thereby, in case that a distribution fee for the information is charged, this is disadvantageous to the user.